Kopsia dasyrachis

Rhazinilam was found to be an oxidative artefact derived from the unstable natural 5,21-dihydrorhazinilam 25 [58,59,60]. Other compounds of the (-)-rhazinilam series have been isolated from various Apocynaceae. (-)-3-Oxorhazinilam 26, also called rhazinicine, was founded in Kopsia dasyrachis Ridl. [63] and in hybrid plant cell cultures [64]. 

Kopsia profunda and Kopsia dasyrachis are sources of new dehydropleiocarpine-type alkaloids which are characterized by the presence of a double bond across the C(16)/C(17) bridge. Alkaloids of this group include kopsidasine (212) and its Moxide (213) from K. dasyrachis [158] and MO tnethoxycarbonyl-l 1,12-niethylenedioxy-A -kopsinine (214), MI)-niethoxycarbonyl-l2-methoxy-A -kopsinine (216), and /V( I )-niethoxycarbonyl-12-hydroxy-A -kopsinine (218), and the A -oxides of 214 and 216 (215 and 217, respectively) from K. profunda [159,160]. These alkaloids show the typical olefinic carbon resonances as well as the vinylic-H resonance associated with the acrylic ester moiety. A similar compound, kopsijasmine (219) has also been obtained from the Thai species, K. Jasminiflora [150]. 

Kospsidasinine (229) was first isolated from Kopsia dasyrachis collected from Sabah in Malaysian Borneo. The structure was established by a combination of spectroscopy and chemical correlation, in particular, the key observation that the Hofmann degradation product of kopsidasinine, 232, was identical with the product obtained by treatment of kopsidasine (212) with methyl iodide [158]. Only two other kopsidasinine-type alkaloid have since been reported, 12-methoxy-lO-demethoxykopsidasinine (230) from K. pauciflora [116] and 10-demethoxykopsidasinine (231) from the Thai species, K jasminiflora [161]. A distinguishing feature of these compounds is the presence of a relatively low field pair of AB doublets (5 4.0 and 3.5) due to an isolated CHCH unit corresponding to C(16)-C(17) and an unusually low field ketonic carbon resonance (5 214) due to C(21) [116,161]. 

A new monoterpene alkaloid, kinabalurine G (330) has been obtained from the leaf extract of Kopsia dasyrachis in addition to 11 known alkaloids and the novel pentacyclic indole, danuphylline vide infra) [223]. Analysis of the spectral data allowed assignment of the gross structure as well as determination of the stereochemistry at the various centers. Kinabalurine G (330) is the AZ-oxide of 9-hydroxy-S-skytanthine, which is unknown, although a 9-hydroxy-skytanthine of unknown stereochemistry has been previously reported from Tecoma stans [224]. 

The stem extract of Kopsia dasyrachis furnished a total of 32 alkaloids. In addition to the new alkaloids mentioned earlier (vide supra), other new alkaloids include, the A (4)-oxides of kopsiflorine (351) and 11-methoxykopsilongine (352), decarbomethoxykopsifine (353), kopsinarine (354), 11,12-methylenedioxykopsine (355), dasyrachine (356), and (-)-l9(J )-hydroxyisoebumamine (357) [234]. 

The leaves of Kopsia dasyrachis (Apocynaceae) afforded an alkaloid, kopsirachine, derived from units of catechin (75) and two units of skytan-thine (58). By mass spectrometry, the molecular weight was established as 620 amu, and the UV spectrum (256 and 281 nm) indicated a relationship to catechin. The major fragment in the mass spectrum appeared at m/z... 

Catechins are particularly good nucleophiles, so it is not surprising to find these compounds substituted at the A-ring with other natural products. The bark of Quercus stenophylla contains ellagitannins that are linked by carbon carbon bonds to the C-6 or C-8 of catechin (277). Kopsirachin (25), from Kopsia dasyrachis, is a most interesting example of this type of catechin derivative in which both the C-6 and C-8 positions are substituted by the alkaloid skytanthine (160). Other examples of this type of compound are the C-6, C-8, and C-6 -l- C-8 cinnamate derivatives of catechin isolated from Cinchona succirubra (273, 279). It can be predicted that many more examples of this type of catechin derivative will be found in the future. 

Homberger K, Hesse M 1984 Kopsirachin, ein ungewohnliches Alkaloid aus der Apocynaceae Kopsia dasyrachis Ridl Chim Acta 67 237-247... 

Kopsia dasyrachis (Apocynaceae) Kopsia dasyrachis (Apocynaceae) Cinchona pubescens (Rubiaceae)... 

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